Methods to repair well liner hangers

ABSTRACT

Methods to repair leaking liner hangers and/or drop off liner assemblies utilizing heaters to melt metal alloys which will solidify and form an annular seal at the liner hanger and seal the leak. Such methods may be used in numerous liner hanger environments, including but not limited to, well bores with and without tieback assemblies.

CROSS-REFERENCE TO RELATED APPLICATION

None

BACKGROUND OF THE INVENTION I. Field of the Invention

The present disclosure relates generally to the repair of well liner hangers, and more particularly to methods utilizing chemical heaters to melt metal alloys which will cool and solidify to form an annular seal at a liner hanger, liner packer, liner top sub of a drop-off liner, or at the top of a leaking cement column adjacent to a liner hanger in a subterranean well bore.

II. Description of the Prior Art

Essentially, the basic sequence of events for the construction of a well used for oil, gas, etc. consists of drilling a stage to a certain depth, running casing, and then cementing the casing in place. The subsequent run is deeper but of a smaller diameter. The borehole size and the casing size get smaller as each run is placed moving down the well. Large casing sizes are used at the top of well bore geometries to isolate shallow aquifers, stabilize the bore hole, and provide a bushing commonly referred to as a drilling liner. Extra intermediate casing strings are used in the event of drilling difficulties or the need to cement the well in stages. The last casing string in the well is usually the production liner after which the production tubing and completion equipment are landed. After this construction phase the well will be used for evaluation and eventually production or injection. Later in the life of the well, there might be a need to plug the well either temporarily or permanently in one of many different locations or geometries.

Liner Hangers are used to hang long heavy sections of casing or tubing in a well and are normally located in the well after casing and cementing several larger casing strings. The deeper and smaller sections of casing are often called liners or production liners. Liners may or may not be cemented in place at the time that the liner hanger is installed. Most liner hangers include casing slips with so-called wickers made by hardened teeth used to penetrate the inner surface of the casing. The slips are supported with wedges or cones to anchor the liner string to the next larger casing string.

If casing slips are not included in the liner hanger it may contain expandable components that are expanded during the setting process. This process is used to compress annular seal packages and form a high friction fit inside the casing. There are many different designs for the annular seal packages located between the liner hanger components and the casing. Some have one or more components made of elastomer or non-elastomeric materials. The packages may include brass, steel, or metal backup mechanisms. Some designs have metal encapsulated seal systems.

In any event, liner hanger seal packages are subjected to harsh conditions such as high fluid velocity during the run in the well, and high forces during cyclic pressure and load conditions experienced during the life of the well. In some instances, the seals are set by axial load applied during the setting process. Unfortunately, in these instances it is not uncommon that the inside of the casing may not be clean and may be covered in drilling mud, cement, cement stringers, well debris, etc. Accordingly, this setting will likely be compromised.

Liner hangers provide several benefits to the well construction phase. For example, casing is installed faster thus reducing the exposure of the formation to drilling fluids and sluffing into the open hole, which will also increase the chance of successful cement job. Additionally, installing a liner hanger to anchor the weight of the liner string reduces the axial load on the well head and will also possibly reduce the load requirements for the rig being used to construct and complete the well.

Liner hangers are designed and sold with many different features. They may or may not include expandable components, casing slips, annular seals, left hand running threads, castellations above the running threads, polished bores, liner packers, or tieback assemblies which include seals in the seal bore and casing to surface. They can be designed and set with different setting methods including mechanical set, hydraulic set or a combination of both. Some have the ability to be rotated after they are set which enhances the ability to get a good cement bond. A drop off liner assembly might contain a liner top sub, a swellable packer, be cemented in place or just dropped off. It is quite common for drop off liners to extend into the horizontal part of the well bore.

Accordingly, liner hanger assemblies are critical parts of the well bore isolation system. Indeed, in some jurisdictions, they are considered so-called barriers by definition and thus deemed to be critical in well regulations. This drives them to be a regulated product requiring rigorous qualification for API and ISO standards that define seal ratings and qualification testing.

There are many possible failure modes of liner hanger assemblies. Historically, cement leaks, and liner hanger leaks occur due to cyclic loading of temperature, pressure and axial loads. If the slip system of a liner hanger fails, the movement of the liner hanger assembly relative to the casing it is set in may case the seal package to extrude and/or fail to hold pressure. Even if the slip system does not fail, the seal system can fail to hold pressure during the life of the well due to fatigue experienced during normal well operations that include cyclic loading. Variations in load can be caused by heating and cooling of the well bore due to production rate changes, formation movement (compaction), as well as ballooning and contraction of tubulars.

These problems have been treated the same way with either cement squeezes or resin injection. Repairing a leaking liner hanger is quite expensive and often includes a great deal of equipment. For example, a work over rig, drilling rig, or a hydraulic work over unit and several runs into and out of the well with a workstring, coiled tubing, and/or electric line.

A cement squeeze treatment requires perforating the tieback above the liner hanger assembly, setting an isolation assembly made up of bridge plugs, or cup seals and/or retrievable packers to isolate the cement flow down the workstring, through the perforations and out to the annular area above the liner hanger between the tieback and the casing. This may not be feasible if the injection rate is not high due to a tortuous path, small leak, limited pump pressure, corroded tubulars, or other factors. After the remediation cement job has been pumped this method requires removing the isolation assembly, excess cement, and well debris after pumping the cement. These steps require several runs with the workstring, coiled tubing and/or electric line. Each run in and out of the well adds costs and risks to the well. Some bridge plug assemblies are retrievable but others are milled up in the final steps of the remediation process.

Resin injection treatment is similar to the cement squeeze process and includes extra costs and risks of special blends, chemical interactions, hardening time, bonding, etc. The resin has advantages over cement in that it can penetrate small openings, run deeper into those openings, and possibly have better control over curing rates when compared to cement.

This disclosure describes a method of using alloys for repairing a liner hanger or liner packer that has been installed in the well. It works for both a liner hanger with no tieback assembly as well as a liner hanger with a tieback assembly running to the surface. In the first scenario, the leaking liner hanger is easier to access. In any event, the alloy will form a metal to metal seal with the outer surface of the liner hanger and the inner surface of the casing. In addition to or in lieu of, the alloy can be used to make a metal to metal seal between the outer surface of the tieback assembly and the inner surface of the casing.

The present disclosure overcomes the disadvantages of presently available methods to deal with leaking liner hangers. Accordingly, it is a general object of this disclosure to provide a method to repair a leaking liner hanger in a well.

It is another general object of the present disclosure to provide a method to perforate into a thermally deformable annular packer (TDAP) and repair a liner hanger.

It is a more specific object of the present disclosure to provide a method to repair a leaking liner hanger using low melting temperature alloys.

It is another object of the present disclosure to provide a method to repair a leaking liner hanger using a low viscosity alloy that can rapidly penetrate small openings prior to changing to a solid state.

It is still another object of the present disclosure to provide a method to repair a leaking liner hanger that readily bonds and forms a seal between the liner hanger outer surfaces and the inner surface of the casing.

Yet another object of the present disclosure to provide a method to repair a leaking liner hanger using an alloy that expands volumetrically during solidification to lock the seal in place.

Still another object of the present disclosure to provide a method to repair a leaking liner hanger wherein the alloy can be melted and the tieback can be pulled from the well when used in an annular seal between the tieback and the casing.

These and other objects, features and advantages of this disclosure will be clearly understood through a consideration of the following detailed description.

SUMMARY OF THE INVENTION

According to an embodiment of the present disclosure, there is provided a method for repairing a leaking liner hanger consisting of running a well plug below the liner hanger, running service tools including a heater with an alloy in the well above the hanger, starting the heater for melting the alloy and plugging the leaking liner hanger, and pulling the service tools from the well.

According to an embodiment of the present disclosure there is also provided a method for repairing a leaking liner hanger having a tieback consisting of running a well plug below the liner hanger, perforating the tieback, running service tools including a heater with an alloy in the well above the hanger, starting the heater for melting the alloy and plugging the leaking liner hanger, and pulling the service tools from the well.

According to an embodiment of the present disclosure there is also provided a method for repairing a leaking liner hanger having a tieback and a TDAP consisting of running a well plug below the liner hanger, perforating the TDAP, running service tools including a heater with an alloy in the well above the hanger, starting the heater for melting the alloy and plugging the leaking liner hanger, and pulling the service tools from the well.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will be more fully understood by reference to the following detailed description of one or more preferred embodiments when read in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout the views and in which:

FIG. 1 is a well schematic view with several casing sizes run to different depths and includes one liner hanger assembly.

FIG. 2 is a well schematic view with several casing sizes run to different depths and includes a tieback assembly and one liner hanger.

FIGS. 3A-3C are well schematic views that illustrate a sequence used to install a metal alloy seal in a well at a leaking liner hanger according to the principles of the present disclosure.

FIGS. 4A-4C are well schematic views that illustrate a sequence used to install a metal alloy seal in a well at a leaking hanger having a tieback assembly.

FIG. 5 is a well schematic view illustrating a plug installed and service tools.

FIG. 6 is a well schematic view illustrating an installed plug, service tools and an alloy seal placed at the liner hanger assembly.

FIG. 7 is a well schematic view illustrating an installed plug with an alloy seal, service tools and a tieback assembly perforation just above the liner hanger.

FIG. 8 is a well schematic view illustrating a TDAP on the outer surface of a casing joint or pup joint in the tieback assembly.

FIG. 9 is a well schematic view illustrating a plug, seal, service tools and a tieback assembly perforation above the liner hanger.

FIG. 10 is a well schematic view illustrating the liner hanger, seal, and perforations in the wall of the tieback that have been filled with alloy to form a pressure tight seal.

FIG. 11 is a well schematic view illustrating a simplified enlarged scale of a heater and electric line according to the principles of the present disclosure.

FIGS. 12A-12D are quarter cross-sections that illustrate a sequence of events placing the alloy on the outer surface of a drop off liner according to the principles of the present disclosure.

FIG. 13 is an enlarged quarter section cross-section of the drop off liner assembly and service tool string parts of F13 of FIG. 11 .

FIG. 14 is a simplified logic flow process diagram of the methods according to the principles of the present disclosure.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

One or more embodiments of the subject disclosure will now be described with the aid of numerous drawings. Unless otherwise indicated, use of specific terms will be understood to include multiple versions and forms thereof.

There are many types of liner hanger assemblies that have been developed for the oil field industry. These include, but are not limited to; expandable, those containing slips only, those containing slips and annular seal packages, those with expandable components, those with liner packers, etc. It will be appreciated that the methods disclosed herein can be applied to any and all types of liner hanger assemblies.

Turning now to the Figures, and in particular FIG. 1 , a simplified cross-sectional underground schematic for casing in a well is shown In general, the initial borehole is drilled into the surface 10 at a first diameter 12 and a first depth 14. A first casing 16 is then run the same depth 14 and cemented in place. A second borehole is drilled at a second diameter 18 to a second depth 20. A second casing 22 is then run the same depth 20 and cemented in place. Numerous subsequent boreholes may be needed dependent upon the individual well environment and requirement. These run stages will get smaller in diameter the deeper the depth. Each casing string will have a shoe on the bottom which cement can be pumped through to cement the casing in place sealing between the outside of the casing and the inside of the borehole. The deep and smaller casing, the so-called liner 24 does not extend all the way back to the surface 10. The liner hanger 26 is used to hang these long and heavy sections of casing 24.

The remediation method to repair a leaking liner hanger 26 in FIG. 1 involves running in the well one or more service tool string trips to isolate the inner diameter (ID) 28 of the hanger assembly, melt a metal alloy, allow it to run down to the liner hanger, cool, solidify, and form an annular seal. If the well is to be plugged at the liner hanger, that can be accomplished with an alloy plug across the desired diameter, either above, below or across the liner hanger or in any combination thereof.

FIG. 2 shows the same schematic as FIG. 1 , but it includes a tieback assembly 30 from the liner hanger 26 to the casing hanger (not shown) located at the top of the well. In this schematic the casing 24, the liner hanger 26, and the tieback 30 is often referred to as a production liner 32 as it is capable of withstanding rigorous pressure loads applied during the well testing performed after the well has been constructed. It is important to note that the tieback is not typically cemented in place and well integrity depends on the liner hanger to seal against the next larger casing size. In some instance this liner hanger begins to leak during the life of the well.

The remediation method to repair a leaking liner hanger 26 in FIG. 2 involves running in the well one or more tool string trips to perforate the tieback assembly 30, melt alloy, allow it to run down to the liner hanger 26, cool, solidify, and form an annular seal. If the liner assembly does not include a liner hanger the liner top sub and the casing can be used as boundaries to form the annular, alloy, metal to metal seal.

FIGS. 3A, 3B, and 3C show a sequence and method used to install a metal alloy seal in a well at a leaking liner hanger. FIG. 3A, and more particularly FIG. 5 , show a leaking liner hanger assembly installed in a well. FIG. 3B shows a leaking liner hanger assembly and a service tool string 34 run in the well on electric line 36 including a heater 38 with alloy cast on its outer surface and an isolation member 40 set inside the liner hanger assembly. This isolation member may include a plug, a seal or a combination thereof to isolate the inside of the liner hanger. This will contain all or a majority of the liquid alloy to the area above the liner hanger or between the liner hanger outer surfaces in order to make the annular seal. FIG. 3C, and more particularly FIG. 6 , show a repaired liner hanger assembly with an annular, metal alloy seal 42 above the liner hanger 26. The annular seal might be placed above the liner hanger or above and between the liner hanger outer surfaces and the inner surface of the casing or between the liner hanger outer surfaces and the inner surface of the casing.

Prior to arriving at the well the alloy used to make the seal is either cast on the heater body or carried in the heater assembly under a cover. The running of service tools can be performed utilizing CTbg, slick line, electric line, or other run on pipe methods as known in the art. For the methods described herein, the starter assembly has been made up to the heater assembly and is considered part thereof. There are several different starter variations which utilize different communication methods including direct electrical connection with the electric line 36, a delay timer, or a pressure sensor. Each starter design receives a signal, and includes a method of starting the chemical reaction in the heater 38. These types of mechanisms relating to oil field tools run on electric line, slick line, coiled tubing, and jointed tubing are well known in the art. The alloy used is a eutectic, metal alloy or a bismuth based alloy or a low melting temperature material and are also well known in the art. The electric heater is only viable if the well is shallow, fairly warm and the volume of alloy to be melted is small. In these conditions and all others it will be best to use one or more chemical heaters to provide heat energy.

The particular method to repair a leaking liner hanger assembly a s shown in FIGS. 3A-3C, and FIG. 5-6 include: re described in FIGS. 3A, 3B, 3C and 5 . The process steps are: running the plug 40 in the well and setting it at the desired depth 44 below the surface; running the heater 38 in the well with electric line 36 (note the alloy is installed on or in the heater before run in the well); sending the signal to start the heater 38; heating the alloy and allowing it to run down to the liner hanger assembly 26, where it will cool, and solidify form a seal as shown in FIG. 6 ; and pulling electric line 36 and heater 38 out of the well.

FIGS. 4A-4C show a sequence and method used to install a metal alloy seal in a well with a tieback at a leaking liner hanger. FIG. 4A shows a leaking liner hanger assembly with a tieback assembly installed in a well. FIG. 4B shows a leaking liner hanger assembly and a service tool string run in the well on electric line 36. The service tool string includes a heater 38 with alloy cast on its outer surface and a plug 40 set inside the liner hanger assembly. FIG. 4C, and more particularly FIG. 7 show a repaired liner hanger assembly with an annular, metal alloy seal 42.

The particular method to repair a leaking liner hanger assembly with a tieback as shown in FIGS. 4A-4C and FIG. 7 include: running the plug 40 in the well and setting it at the desired depth 44 below the surface; running the perforating guns in the well to the desire depth, firing the guns thereby making perforations 46 in the tieback 30 assembly above the liner hanger 26; running the heater 38 in the well with electric line 36 (note the alloy is installed on or in the heater before the heater arrives at the well site); sending the signal to start the heater 38; heating the alloy and allowing it to run down through one or more perforations 46 located in the tieback assembly 30 to the liner hanger assembly 26, where it will cool, and solidify form a seal as shown in FIG. 7 ; and pulling electric line 36 and heater 38 out of the well.

Referring back to FIG. 7 , the annular seal 42 can be placed above the liner hanger 26 and the casing or between the outer surfaces of the components that make up the liner hanger 26 and the casing or both of these scenarios. If the liner hanger 26 assembly includes an annular seal package that will make a good stop point for molten metal alloy as it runs down the well in its molten state. The plug 40 could be any plug available, but the preferred assembly is a bridge plug that can be run in the well with electric line 36 and an electric line setting assembly. The alloy can be placed in the well in a couple of different ways. The alloy can be run in the well with the heater 38 assembly or alloy beads can be carried into the well and released from a dump bailer and allowed to fall to the target depth or the alloy beads can be dropped from the surface down the annular area or inside tubing to land at the intended target. Alternatively, a combination of these methods can be used.

If a tieback has a metal alloy annular seal between the outer surface of the pipe and the inner surface of the casing, this can be melted by heating the inside of the pipe. Once melted, the tieback can be retrieved. If a drop off liner has a metal alloy annular seal between the outer surface of the pipe and the inner surface of the casing, this can be melted by heating the inside of the pipe. Once melted, the tieback can be retrieved.

A Thermally Deformable Annular Packer (TDAP) is made up of alloy melted and cast on either the inner surface of a pipe or the outer surface of a pipe. It is generally thin enough to allow clearance for running adjacent tubing or cementing around. If it is run in the well on the outer surface of a pipe it does not touch the inner surface of the next larger size pipe. If it is run in the well on the inside of a pipe it does not touch the outer surface of the next smaller size pipe.

If a TDAP is placed on the outer surface of a pup joint, production tube, or casing joint it could be run in the well and used soon after being run in the well or it could be used later in the life of the well. One way to utilize the TDAP is to perforate into it in order to a) make an annular seal between the outer surface of the pipe and the inner surface of the next larger size of pipe or to make an annular seal and a plug across the inside of the pipe the TDAP was run in the well on. Either of these methods would be useful to repair a liner hanger, a liner top packer, a production packer or any other type of annular seal placed in a well including cement. Extra alloy can be added to one or more TDAPS that have been perforated into by adding beads from the surface via circulation into the well, dump bailer runs, or dropping and letting gravity act the dense mass. A heater used in the well to melt the alloy from the TDAP and any other alloy run from the surface. The alloy melts, and moves to the sealing area where it cools and forms an metal to metal seal.

Another embodiment is to use a thermally deformable annular packer as described in U.S. Pat. No. 10,145,203, entitled Thermally Deformable Annular Packers, and incorporated herein by reference. FIG. 8 shows the seal 50 material as a thermally deformable annular packer on the outer surface of a full joint of pipe/casing or a pup joint in the tieback 30 assembly after the perforation(s) 46 have been made through the tieback assembly and into the alloy 50. It will be appreciated that the perforation(s) 46 will be made just before the heater is used to melt the alloy and form an annular seal.

The method here includes: running the plug 40 in the well and set it at the desired depth below the surface; running the perforating guns in the well to the desire depth, firing the guns thereby making perforations into the alloy 50 on the outer surface of the tieback 30 component(s) above the liner hanger 26; running the heater 38 and the alloy in the well with the metal alloy 50 with electric line 36 (note the alloy is installed on or in the heater 38 before the heater arrives at the well site); sending the signal to start the heater 38; heating the alloy to melt it and allow it to run down to the liner hanger 26, cool, and solidify forming a seal 42 (see FIG. 9 ).

This method could be used above a cement sheath, a production packer, annular production seals, or similar geometry, where perforating into a thermally deformable annular packer, heating the alloy and forming a seal would fix a leaking annular area in the well. This method could also be used to plug the inside diameter of the casing or tubing as well for a well plugging operation.

The heater 38 run on electric line may or may not contain more metal alloy. The alloy can be used to form an alloy plug inside the tieback assembly 30. Extra alloy may be carried in with the heater 38 if it is needed to form a plug on the inside of the tieback 30 or the inside of the liner hanger 26. In some instances, this may be beneficial to enhance heat transfer to the alloy in the annular area between the casing 48 and the tieback 30. The alloy on the inside of the tieback 30 and liner hanger 26 can then be milled out leaving a full inside diameter equal to the tieback 30. Also, as alternative or additional steps, alloy beads can be dropped from the surface or a dump bailer and run most of the way down the well to a location above the target.

The thermally deformable annular packer alloy could be used with or without the step of perforating through the tieback into the thermally deformable annular packer alloy. If a BiSN Wel-lok® tool is used inside the tieback 30 to melt the alloy carried in and melted inside the tieback 30, then the plug 40 is optional. Heat would be transferred from the molten alloy inside the tieback 30 through the wall of the tieback and to the alloy on the outer surface. Similarly, an alloy plug may be formed inside the tieback assembly heating the tieback pipe wall and the thermally deformable annular packer on the outside surface. As it melts it will run down the liner hanger forming an alloy seal. The alloy plug on the inside of the tieback can then be removed by milling.

Yet another embodiment includes the thermally deformable annular packer does not include perforating through the tieback assembly. In this instance a very large diameter heater can be run inside the tieback. This may transfer enough heat to melt the thermally deformable annular packer alloy allowing it to melt and run down to the liner hanger.

FIG. 9 shows the seal 42, installed at the liner hanger assembly 26 as well as the liner 24, the casing 48, and the service tools consisting of a heater 38, and electric line 36. The perforations 46 are located in the tieback 30 and above the liner hanger 26. The seal material is a metal alloy, with a low melting temperature, for example an eutectic alloy. It might contain bismuth and other alloying constituents. FIG. 10 shows a sealed hanger assembly with the plug and the service tools of FIG. 9 removed.

In the methods described above, the perforations are filled with alloy. Once the alloy has solidified the tieback 30 becomes capable of holding pressure and the alloy plug 40 on the inside of the tieback 30 can be removed by milling. The thermally deformable annular packer on the outside the tieback can be run in the well at the time of completion. It can be used after the liner hanger is set or it can be used at some point in the future as a contingency plan in the event of a liner hanger leak.

FIG. 11 illustrates a simplified enlarged scale of the service tools used to perform the subject methods of some of the present embodiments. In particular, the heater 38 and electric line 36 therefor is shown within the casing 48 near the drop off liner assembly 52 and within the drop off liner top sub 54. It may be possible to use a set down seal on top of the liner hanger in the well configuration without a tieback. This would allow the liquid alloy to flow into the annular area between the outer surface of the liner hanger and the inner surface of the casing to form an annular seal. If the set down seal will not work due to castellations or other difficult geometry then another type of seal may be required.

In some installations, a drop off liner includes a swellable packer designed to seal the annular area between the drop off liner and the inside of the casing. They often fail, allowing fluid communication. In this event, instead of placing a plug like a bridge plug across the entire inside diameter of the liner hanger assembly a seal can be formed by setting weight down between the service tool assembly and the top end of the liner as shown in FIG. 12B. This involves using a set down seal 56 as shown in FIG. 13 . The seal could be made of an elastomer such as nitrile, hydrogenated nitrile, a fluoropolymer, or a non-elastomeric material like an engineering plastic, a soft metal like copper, lead, bismuth, a bismuth alloy, or another metal alloy. In some instances, the top of the liner top sub will have castellations milled into the upper face. In this case a set down seal could be used inside the liner hanger assembly below the left hand, running threads 58 if transition bevel exists between diameter changes. Alternatively, if the liner hanger assembly includes a seal bore there are many off the shelf seals are readily available including O-ring in a groove, molded elastomeric seals or chevron seals.

More particularly, the quarter section, sequence of FIGS. 12A, 12B, 12C, 12D along with FIG. 13 describe using a seal 60 energized by setting weight down through the service tool to the drop off liner top sub 54. A few parts of the service tool are shown including the seal mandrel 62, seal 60, and the cap 64. The drop off liner includes a liner top sub 54, and liner.

Electric line would be used to run a heater along with the service tool components used to make a seal on the liner hanger top sub or the drop off liner's top sub. Enough weight would be set down to energize the seal. This will eliminate the molten allow from entering the inner diameter of the drop off liner's top sub 54. The molten alloy will cool as it runs down the annular area created by the inside of the casing and the outside of the drop off liner. As it cools it will solidify forming an annular seal. This method could be used with a liner hanger shown in FIG. 5 or with a drop off liner shown in FIG. 12A.

Other options may include installing a thermally deformable annular packer on the outer surface of the drop off liner instead of using a swellable packer. In this case, the run-in well diameter will need to be sufficiently smaller than the casing inside diameter to allow for fluid bypass. Once the drop off liner is placed in the well bore, the thermally deformable annular packer alloy could be melted and cooled forming an annular seal.

Another option may be to run the thermally deformable annular packer on the outer surface of the off liner, then melt it, allow it to cool and form an annular seal between the liner and the inner surface of the casing. This might be a contingency method run in the well with the liner in the event the swellable packer annular seal fails to hold pressure.

A thermally deformable annular packer could be run on a drop off liner with the intent of perforating into it. Those steps are described in detail above. This might be done after placing the drop off liner as a primary annular seal mechanism or as a contingency for a leaking swellable packer, open hole packer, inflatable packer, etc.

In the event that production tubing is in placed inside the tieback assembly it is possible in some combinations of tubing and tieback assembly sizes to perforate through both the production tubing and the tieback assembly and get alloy to form an annular seal between the outer surface of the production tubing, the inner surface of the tieback assembly, the outer surface of the tieback assembly and the inner surface of the casing. Two annuli can be sealed with the metal alloy depending on heater size, well temperature, well bore fluids, perforation sizes, perforation penetration depth and metal alloy composition. The perforations in the tubing and tieback are sealed with alloy and they are capable of holding pressure.

In another embodiment, a joint of casing, pipe, or a pup joint would have alloy seal material cast on its outer surface prior to arriving at the well. It would be run with the casing just inside the bore hole. The casing string may or may not be cemented in place prior to cementing. If the cement sheath begins to leak at a future date, a perforating gun could be run into the well, fired making a perforation through the casing and into the alloy on the outside surface of the casing or pup joint. A heater would be run in the well on electric line, slick line, coiled tubing or jointed tubing depending on the heater starter method chosen. The assembly would be run to the target depth, the signal to the start the heater would be sent, the alloy melted, where it would run to any void areas, cooling down, solidifying and creating a seal.

The thermally deformable annular packer could be installed on a casing joint, or pup joint and run in the well on a drop off liner assembly. These are not typically run with full liner hanger assemblies with slips or optional annular seal packages. In some configurations a swellable packer is run below the liner top sub. If the swellable packer leaked after installation or at some point after that the well operator would have the ability to make a seal between the outer surface of the liner assembly and the casing by running into the well with electric line or another means and a heater to heat, melt, and make an annular seal with the alloy.

If it was desired to plug and abandon, placing the plug in the tieback assembly above the liner hanger as shown in FIG. 2 , a thermally deformable annular packer could be installed on a casing joint, or pup joint and run in the well as part of the tieback assembly.

A chemical or electrical heater will be used to melt the alloy which runs down the well to the liner hanger where it will form an annular seal. A perforating gun can be used to perforate through the pipe and into the thermally deformable annular packer before the heater is used to heat the alloy. Then it will run down the well to the liner hanger where it will form an annular seal. Depending on the casing sizes, tubing size, well depth, and well temperature it may be possible to run the heater inside the joint(s) or pup joint(s) which contain the thermally deformable annular packer, heat it from the inside without the need to perforate it. After the alloy is melted it will run down well to the liner hanger where it will form an annular seal.

If the tieback is cemented in place, the perforating operation can be used to perforate the pipe wall of the tieback and into the cement, creating fractures that can be used as paths for the alloy to travel through to get to the liner hanger. If production tubing is installed inside the tieback assembly, it may be possible to perforate the production assembly, the tieback, and get alloy to the liner hanger depending on well depth, liner hanger depth, well temperature, the size of the production tubing, the size of the tieback and the volume of alloy required to form the annular seal.

Alloy could be cast on the outside diameter of any one or multiple liner hanger components. The alloy could be placed in a groove on the outer surface of the liner hanger before it is run in the well. The outside diameter of the alloy would allow enough annular flow area to run the liner hanger in the well without causing damage to the formation, well, or equipment in the well.

The described methods herein have included a plethora of variations for repairing a leaking liner hanger in a well bore. FIG. 14 will illustrate a simplified logic flow 66 of these methods in diagram form. In particular, the process starts 68 upon a review/maintenance/check it is determined whether the liner hanger has a leak 70. If not, the process ends 72. If so, the proper process is then determined by whether 74 there is a tieback in the well. If there is not a tieback within the well, then the plug will be set 76 at the required depth and the service tools will be run 78. A calculation is made to determine whether 80 additional alloy will be needed for the repair. If so, then this additional alloy may be supplied 82 via beads from a dump bailer or from the surface. In any event, the heater is then started 84 to melt the alloy to seal the leak. The service tools are then removed 86 and it is determined whether 88 the inner diameter (ID) of the well needs to be opened. If so, it is milled 90, the repair work is complete 92 and the process ends 72.

Turning back to the determination 74 of a tieback well, the next step depends 94 on the presence of a TDAP. If not, the plug will be set 96, the tieback will be perforated 98 and the service tools will be run 78. If there is a TDAP, then it needs to be determined if the TDAP needs to be perforated 100. If not, then a large heater or a heater with alloy and a skirt will need to be run 102 before the heater can be started 84. If the TDAP needs perforation, then the plug is set 104, and the TDAP is perforated 106 before the service tools are run 78.

The foregoing detailed description has been given for clearness of understanding only and no unnecessary limitations should be understood therefrom. Accordingly, while one or more particular embodiments of the disclosure have been shown and described, it will be apparent to those skilled in the art that changes and modifications may be made therein without departing from the invention if its broader aspects, and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the present disclosure. 

We claim:
 1. A method for repairing a leaking well liner hanger consisting of: running an isolation member in a well generally proximate to the liner hanger; running service tools, including a heater and an alloy, in said well above said liner hanger; starting said heater; melting said alloy; sealing the leaking hanger; and pulling said service tools from said well.
 2. The method as defined in claim 1 wherein said heater is a chemical heater.
 3. The method as defined in claim 1 wherein additional alloy is added to a sealing area from the surface.
 4. The method as defined in claim 3 wherein said additional alloy are alloy beads.
 5. The method as defined in claim 1 further including milling an inside diameter of said well.
 6. A method for repairing a leaking well liner hanger having a tieback consisting of: running an isolation member in a well generally proximate to the liner hanger; perforating the tieback; running service tools, including a heater and an alloy, in said well above said liner hanger; starting said heater; melting said alloy; sealing the leaking hanger; and pulling said service tools from said well.
 7. The method as defined in claim 6 wherein said heater is a chemical heater.
 8. The method as defined in claim 6 wherein additional alloy is added to a sealing area from the surface.
 9. The method as defined in claim 8 wherein said additional alloy are alloy beads.
 10. The method as defined in claim 6 further including milling an inside diameter of said well.
 11. A method for repairing a leaking well liner hanger having a tieback and one or more TDAPs consisting of: running an isolation member in a well generally proximate to the liner hanger; perforating the tieback and one of said TDAPs; running service tools, including a heater and an alloy, in said well above said liner hanger; starting said heater; melting said alloy; sealing the leaking hanger; and pulling said service tools from said well.
 12. The method as defined in claim 11 wherein said heater is a chemical heater.
 13. The method as defined in claim 11 wherein additional alloy is added to a sealing area from the surface.
 14. The method as defined in claim 13 wherein said additional alloy are alloy beads.
 15. The method as defined in claim 11 further including milling an inside diameter of said well.
 16. The method as defined in claim 11 further including perforating multiple TDAPs.
 17. A method for repairing annular seals in a well bore having a TDAP consisting of running an isolation member to a target area within the well, perforating the TDAP, running service tools including a heater and an alloy, starting the heater, melting the alloy, sealing the annular seal, and pulling the service tools. 